How Web Pages Work
Creating Web pages does not really require any technical knowledge about how the Web works. But it is quite useful all the same to have a general idea of the process - this makes it easier to understand how things are done, and why things sometimes don't work. It will also help you understand the technical limitations of the Web, and the impact this has on what counts as good or bad design.
Each Web page is stored on what is called a Web server. For your own pages this will be the computer belonging to your Internet provider with enormous amounts of disk space, parcelled out between all the subscribers. A large organization, however, may well have its own server (and the requisite staff to maintain it).
When you access a Web page with your Web browser, the browser contacts the server on which the relevant page is stored, via your Internet connection, and requests the page. The server then responds by transmitting the page to your machine - see the box below for a more detailed description of what happens - or sending an error message saying why it can't fulfil the request. The browser looks at what it receives and turns it into a screen display.
Web pages look like a form of desktop publishing but they are in fact created in a completely different way. Rather than being a complex data file, each Web page is simply a plain text file which contains:
Tags are also used to indicate the location of images, and links to other Web pages.
Images are not actually stored in the pages. Each image on a page is stored as a separate file, and the page contains tags which tell the browser which image files to fetch and display. This is why you can "turn off" the images on your browser - it simply doesn't bother to fetch them.
Links, too, are indicated by tags: the hot spot is simply tagged with information about which page to fetch when you click on it with the mouse.
Browsers provide a facility for looking at the plain text file which underlies a page. Look for an option with the word "source" in it (in Internet Explorer and Netscape browsers this is on the View menu).
The advantage of this way of working is that, as text files, Web pages can be looked at and edited on any type of computer: pages created on one type of computer can be viewed or edited on any other without requiring special file conversion utilities such as are needed to convert between word-processor or desktop publishing formats.
Also, it means that you do not need any specific piece of software or even any particular level of hardware to create the pages. As long as a computer has a basic text editor, it can be used to edit pages. Another advantage is that text files are small and can be transmitted very quickly over the Internet, whereas images and word-processor files are much larger, and take correspondingly longer.
The tags used in Web pages indicate how text should look only at a very general level. Rather than specifying, for example, "18 point Optima Bold Italic" for a heading, which would be completely useless for readers without that font installed on their machine, a Web page tag would indicate, say, a "Heading 1" style, and leave it up to the browser to decide which font and point size to use. This is called logical markup (or "semantic markup"): the page creator indicates the function of a piece of text on the page, rather than describing exactly how it will look to the reader (which is descriptive markup). When you put "Heading 1" tags around a piece of text, what you're saying to the browser is, "I don't care how you do it but make sure that this piece of text is the largest heading on the page."
This means that the designer of the Web page specifies the contents and overall structure of the information on the page, but the browser make the final decision on the presentation.
Browsers allow the user to specify certain defaults, so that if you have poor eyesight or a small screen you can configure your browser to use a larger font size - the page designer doesn't need to do a special "large print" version of the page.
Likewise, if you prefer white text on a black background, you, as the reader, can use that combination, over-riding any colour scheme chosen by the page designer. If, for any reason, a browser can't cope with a particular feature it finds on a page, it will do the best it can or simply ignore it, and the content of the page will generally be unaffected.
 On text only browsers, such as the lynx browser for the UNIX operating system, the browser has no access to any other fonts, and will use underlining or a different colour to indicate headings and othe font changes. See how part of this page looks in lynx.